kellito
f5baa05d4a
Add O_NONBLOCK handling to UserInner::call_inner for Opcode::OpenAt. When the caller passes O_NONBLOCK in the open flags and the provider has not yet responded after one scheduling quantum, return EAGAIN immediately instead of blocking the caller. This implements Design B from local/docs/INITNSMGR-CONCURRENCY-DESIGN.md, enabling the initnsmgr to use O_NONBLOCK on openat to avoid head-of-line blocking on slow provider daemons. The mechanism: 1. Detect O_NONBLOCK + OpenAt from sqe.args[3] (flags). 2. For nonblock open, skip the block() call - stay Runnable. 3. Send the SQE and trigger the provider event (same as blocking). 4. Do one context::switch() to give the provider a chance to run and respond. If the provider responds within that quantum, return Ok(result). 5. If the provider has not responded, cancel the request via the existing cancellation path (Cancel SQE + cleanup of callee_responsible PageSpan and fds), and return EAGAIN. The caller treats EAGAIN as 'try again later' and parks the request; initnsmgr (in local/sources/base) implements the event-driven deferred retry pattern that uses this signal. Preserves all existing behavior for non-open opcodes and for open without O_NONBLOCK. Round-robin scheduler means the provider gets a fair chance to run after the caller yields. Per local/AGENTS.md: - No new branches (work on submodule/kernel) - No stubs, no todo!/unimplemented! - Cross-module change: kernel + base (committed separately) Closes v5.3 Design B (kernel side). Base side is the companion commit on submodule/base.
Kernel
Redox OS Microkernel
Requirements
nasmneeds to be available on the PATH at build time.
Building The Documentation
Use this command:
cargo doc --open --target x86_64-unknown-none
Debugging
QEMU
Running QEMU with the -s flag will set up QEMU to listen on port 1234 for a GDB client to connect to it. To debug the redox kernel run.
make qemu gdb=yes
This will start a virtual machine with and listen on port 1234 for a GDB or LLDB client.
GDB
If you are going to use GDB, run these commands to load debug symbols and connect to your running kernel:
(gdb) symbol-file build/kernel.sym
(gdb) target remote localhost:1234
LLDB
If you are going to use LLDB, run these commands to start debugging:
(lldb) target create -s build/kernel.sym build/kernel
(lldb) gdb-remote localhost:1234
After connecting to your kernel you can set some interesting breakpoints and continue
the process. See your debuggers man page for more information on useful commands to run.
Notes
-
Always use
foo.get(n)instead offoo[n]and try to cover for the possibility ofOption::None. Doing the regular way may work fine for applications, but never in the kernel. No possible panics should ever exist in kernel space, because then the whole OS would just stop working. -
If you receive a kernel panic in QEMU, use
pkill qemu-systemto kill the frozen QEMU process.
How To Contribute
To learn how to contribute to this system component you need to read the following document:
Development
To learn how to do development with this system component inside the Redox build system you need to read the Build System and Coding and Building pages.
How To Build
To build this system component you need to download the Redox build system, you can learn how to do it on the Building Redox page.
This is necessary because they only work with cross-compilation to a Redox virtual machine, but you can do some testing from Linux.
Funding - Unix-style Signals and Process Management
This project is funded through NGI Zero Core, a fund established by NLnet with financial support from the European Commission's Next Generation Internet program. Learn more at the NLnet project page.
